The present invention relates to a wild rice seed, a wild rice plant, a wild rice variety and a method for producing a wild rice hybrid seed.
Wild rice, Zizania palustris L. (Dore), is an important cultivated specialty crop in Minnesota and California. Despite having "rice" as part of its name, wild rice Zizania palustris L. (Dore) is very different and distinct from domestic or white rice (Oryza sativa L.). The name "wild rice" arises from its aquatic growth habit. Wild rice, the only cultivated species in Zizania, has a chromosome number of 2n equal to 30, while cultivated rice has 2n equal to 24 chromosomes.
Consumption of processed wild rice has grown steadily at 10% to 15% per year since wild rice cultivation began in mid-1960's. As well as direct retail sales, wild rice is used as a supplemental ingredient by numerous large food companies. Total crop value in 1991 at farm level was approximately $20 million.
Wild rice is a paddy-grown crop, adapted to cooler temperatures and deeper water than domestic rice (Oryza sativa L.). This allows wild rice production in Minnesota and parts of California, where rice or other cereals are not adapted. Wild rice in California is grown without the use of pesticides or herbicides. The crop possesses sufficient vigor that competition and good water management are sufficient to suppress weeds. This is important because of the difficulty in obtaining chemical registrations for specialty crops and because it contributes to an overall reduction in pesticide use. Wild rice is widely used to add variety and contrast in flavor, texture, and color to grain-based dishes (rice, pasta, etc). The wild rice grain is nutritious, is relatively easy to prepare for eating, and has excellent storage properties.
In the mid-1980's, competition between newly developed California production and Minnesota resulted in a dramatic decline in wild rice prices. New products containing wild rice as an ingredient increased rapidly during this period. Production efficiencies have since allowed both regions to adjust to the new market conditions. Incremental growth in wild rice production will occur as a result of promotional activity and incremental productivity gains. However, a higher level of productivity is needed to reduce the cost of wild rice production and to promote new uses of wild rice.
Wild rice has numerous unusual seed properties (Kovach, D. and Bradford, K., Temperature Dependence of Viability and Dormancy of Zizania palustris var interior seeds stored at high moisture contents, Annals of Botany, 1992; Kovach, D. and Bradford, K., Imbibitional damage and desiccation tolerance of wild rice Zizania palustris seeds, Journal Experimental Botany, 1992). Wild rice seeds have the following properties: a) a short life in commercial storage (1-2 years); b) die if they are allowed to dry out below about 25%, and c) have a deep, intractable dormancy at harvest. These factors combine to hinder development of a wild rice seed industry, and these characteristics have been the focus of much of the public research on wild rice. Also, the cropping patterns in Minnesota and parts of California rely on volunteer reseeding for establishing crop stands. Because of this, these areas have difficulty adopting new varieties.
Past progress in breeding wild rice has been achieved through population improvement, both in California by Nor-Cal, Inc. and in Minnesota by the University of Minnesota (Everett, L. A. and Stucker, R. E., A Comparison of Selection Methods for Reduced Shattering in Wild Rice, Crop Science 23:956-960, 1983). The high degree of variability encountered suggests that some continued progress can be made through these methods (Foster, K. W. and Rutger, J. N., Genetic Variation of Four Traits in a Population of Zinzania aquatica, Canadian Journal of Plant Science 60:1-4, 1980). Currently the commercial production of hybrid wild rice is not feasible for a number of reasons. However, the development of a hybrid wild rice would greatly accelerate the usage of this crop and could increase both yield and quality characteristics.
Producing hybrids based on a Cytoplasmic-Genetic Male Sterility (CGMS) system has been used in several crops other than wild rice. For example, sorghum seed is produced by CGMS. The use of hybrids in several cereal crops has failed due to the lack of one or more important characteristics. For example, commercial oats and rye are not hybrids. Extensive efforts to develop hybrid wheat and barley have largely been abandoned due to a low level of heterosis and difficulty of developing good restorer lines. Hybrid rice is important in certain parts of parts of the world including China but has not gained a significant foothold in the U.S., despite considerable public and private research efforts. Lack of success in these crops is attributable to one or more of the following: a) insufficient heterosis, b) poor fertility restoration in the hybrid, c) complicated genetics of fertility restoration, and d) difficulty in obtaining the pollen distribution necessary for seed production.